Method of forming metal bonded abrasive articles



Feb 26, 1945 I. B. c. CHANDLER ET Al. 2,395,461

METHOD OF FORMING METAL BONDED ABRASIVE ARTICLES Filed April 20, 1944 ve`n'tion, disc which Figure 1 is Patented F eb. 26, 1946 METHOD oF FoRMrNo Marax. norman .massive narrows Bruce C. Chandler, Waukegan, and William Oscar Bell, Libertyville, Ill., assignors to Pfanstielxl Chemical Company, a corporation of Illinois appiieauoa prix 2c, 1944, serian No. 531,928

. 2 Claims.

This invention relates to a die block and a method of pressing cylindrical objects therein and more particularly to a method of forming diamond dust discs.

The formation of suitable drilling materials from diamond dust particles has long presented a serious problem. In the co-pending application of Bruce C. Chandler and William Oscar Bell, Serial No. 503,938, filed September 27, 1943, a method of forming highly satisfactory diamond dust drills with a-powdered metal binder is described. In that method the material' is formed to suitable shape within a rubber die.

'I'hat method, however, is not adaptable to alishapes of drills', particularly to thin cylindrical drills.

v The ordinary die is duite unsuitable for pressing s uch cylinders not only because ci' the lack of adhesiveness of the diamond particles but because the metal ltends to clog and bind in the die cavities. In accordance with the present inshaped drills are formed within a cylindrical die cavity after which the side walls -of the cavityare moved axially of the cylinder to clear one end thereof while retaining pressure on the disc, after which pressure is released.

'I'he invention is illustrated in the drawing in a vertical elevation partially in section of a suitable apparatus for carrying out the invention; Figure 2 is a similar view after pressure has been' applied to the plunger; and

Figure 3 is a similar view after the stripping apparatus has been actuated to strip the side walls from the cylinder; Figure i isa similar partial view after pressure has been released; and Figure 5 is a partial sectional elevation along the line .s-sin rig. i.

The device comprises a suitable metal base i Acontaining' an adjustable block or plug il, the

upper face of which serves as the bottom of the die cavity. A top support Il is carried on the base by a series of supporting tubes |3`and is secured thereto by a suitable number of clamping screws il. The die bushing l surrounds the upper end. of the block il and denes the side walls of the die cavity. The die bushing is provided with a collar la at its base whichlimits the upward movement of the bushing by engagement with the top support il. A spring l2 normally urges the die bushing against the top support i6. A top platform i6 is carried on an annular shoulder isb of the die bushing. There is suillcient clearance between the platform I8 and the support l to permit the desired movement of the die bushing'.

The necessary pressure for forming the discs is provided by a plunger I8 which is suitably actuated in any desired manner. The plunger is carried in a frame 22 which also carries a stripping fork 2|, and a stripping cam 23 mounted on a stripping shaft 24. A lever 25 is mounted on the stripping shaft and is normally held up` by the spring 26. It will be noticed that on downward movement;v of the lever 2B the cam 28 is brought into engagement with the stripping fork 2| and forces it downwardly against the stripping member I9. A set screw 20 is provided in the frame 22 to hold the plunger in position therein. v

In operating the device, the die cavity 28 isfilled with a suitable mixture of powdered metallic binder, such as nickel, and diamond dust in suitable volumetric, relationship. Normally the diamond dust will not occupy more than 40% by volume of the space after compression. Preferably the diamond dust is about 18% by weight and the metal powder about 82% by weight. After the cavity has been approximately filled with the powder, a small amount of nickel powder is scattered on top to avoid crushing the dia- Amonds and to provide a better cutting drill.

as shown in Figure 2. In this motion thelower frame moves away from the stripping fork 2|. On the other hand, the platform i8 and the die bushing i5 are forced downwardly to make up for the compression of the disc. l

After the desired pressure has been applied it is maintained while the lever arm 25 is pressed downwardly, bringing the cam 23 into engagement with the fork 2i and pressing it :against the stripping member i9. This in turn` forces the die bushing i5 still further down, as shown in Figure 3, until the side walls of the die cavity have cleared one end? thereof. When this happens, the disc 30 which has been formed expands slightly so that on release of the pressure, as shown in Figure 4., the disc is carried upwardly by the die bushing and rests on top thereof so that it may readily be removed by the fingers.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations should be understood therefrom.

What we claim as new, and desire to secure by Letters Patent is: v

l. The method of forming a coherent cyllndri' cal body from a iinely divided mass of metal mi diamond dust, which eemheavy pr to the mass While whereby power binder prises applying conning it in a cylindrical chamber, the mass is pressed inteA a coherent body, mcving the side wells from the mass, while maintaining substantially the forming pressure on the mass, wl'lereiox,v the 'cylindrical iaods' expande slightly lateralw. and then releasing the pres (ideal. 33mm. @ly divided nl, WED.

meneer comprises applying heav pressure t the :nass

while confining it in a cylindrical 'chamben whereby the mass is pressedinto e. coherent body, then moving the side gwalls from the mass, while maintaining substantially the forming pressure on the mass, whereby the .cylindrical bodyexpende 'slightly laterally, and then. releasing the C. CHANDLER.

. BUGE 

